The invention relates to a vacuum valve comprising a closure element and a valve housing with a valve opening and with an interior space in which the closure element is arranged, which closure element, in the closed state of the vacuum valve, bears against a valve seat surrounding the valve opening, wherein the valve housing has a housing wall which delimits the interior space and which is comprised of sheet metal and which, to form the valve opening, is provided with a window recess, and wherein the valve opening is surrounded by a flange ring which is connectable by way of screw connections to an attachment flange of a vacuum unit which has an interior space, to which vacuum unit the vacuum valve can be attached.
It is known, in the case of vacuum valves, for housing walls to be formed from sheet metal in order to realize material savings. A vacuum valve of the type mentioned in the introduction emerges from WO 2011/088482 A1 and U.S. Pat. No. 7,011,294 B1. The vacuum valve has housing halves comprised of sheet metal, which form opposite first and second housing walls which are each provided with a window recess for forming a valve opening. A respective side wall of the valve housing is formed by bent sections of the two housing halves, wherein the two housing halves are welded to one another in the region of the side walls. Pipe connectors surrounding the window recesses are welded to the outer sides of the opposite housing walls, to which pipe connectors in turn there are welded solid flange rings. By way of said solid flange rings, which are equipped with passage bores, the vacuum valve can be screwed to an attachment flange of a further vacuum unit, for example of a vacuum chamber or of a pipeline. To provide the valve housing with the required stability, further measures are required; in particular, it is necessary to provide support parts which run between the two flange rings and which support said flange rings against one another, which support parts are welded to the two flange rings. The production of the vacuum valve is thus made more expensive.
Another valve comprised entirely of sheet metal emerges from DE 29 27 369 A1.
Also known are vacuum valves which have a solid valve housing, in the case of which an exchangeable annular insert part is provided within the valve housing. The insert part, which is sealed off with respect to the valve housing by way of a seal, has the valve seat, against which the closure element is caused to bear when the vacuum valve is in the closed state. A vacuum valve of said type emerges for example from JP 2012-72888 A. The closure element is in this case movable rectilinearly between its open position and its closed position, which it assumes when the vacuum valve is in the closed state, wherein the seal arranged on the closure element and the sealing surface arranged on the valve seat have a three-dimensional contour. Further vacuum valves of said type with an exchangeable valve seat are known from prior use. In this case, the valve seat can, from the direction of the interior space of the valve housing, be screwed to the housing wall which has the valve opening by virtue of connecting screws being screwed, through passage openings of the valve seat, into blind threaded bores in the housing wall. The seal between the valve seat and the housing wall is thus compressed. Owing to the removability of the valve seat, it is possible for the valve seat to be exchanged in the event of wear of the valve seat, for example due to aggressive process gases, even with the valve housing of the vacuum valve remaining connected to a further vacuum unit. It is also possible to use valve seats with different surfaces, which are for example resistant to different process gases that are used in different vacuum processes. A further vacuum valve with exchangeable valve seat emerges from U.S. Pat. No. 8,272,825 B2 (cf. FIG. 4A, right-hand side). The insert part which has the valve seat extends in this case through the window recess in the solid housing wall to the outer side of the valve housing, and there, has a seal for shielding the process gas from the flange seal of the valve housing, which flange seal is arranged in a groove of the solid housing wall.